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Related: Is secondhand smoke dangerous? ( thanks JoseK )


I've heard this argument many times, the logic being that the smokers body is used to the toxins inside the cigarettes, which leads to more damage being caused to non-smokers. However, it could also be possible that only a reduced amount of dangerous substances is inhaled via secondhand smoking - which would lead to less damage.

As an example, I have two personal friends. They're brothers: one smokes and the other does not. The smoker often smokes in the proximity of his brother. They recently had their lungs checked, and the non-smokers lungs were in much worse condition than the smokers.

Obviously, that does not imply that the damage was caused by the cigarettes, but is that common? I'm referring to situations when non-smokers spend a lot of time in the proximity of heavy smokers. To rephrase, is it likely that regularly inhaling cigarette smoke could cause the same amount of damage ( or more ) as smoking ?

  • Does this assume smokers hold their breaths between puffs? – RedSonja May 11 '15 at 8:42
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No. You would need to find a mechanism, such as arguing that a smoker breathes in filtered smoke which the person next to them breathes in unfiltered smoke. Since almost all smokers do not have a cigarette in their mouths all the time, this is highly dubious.

The evidence from second-hand smoke studies is that the risk to the non-smoker is small but clear: examples include an odds ratio for non-smokers exposed to long-term spousal smoking of 1.23 (95% CI = 1.01-1.51) compared with those not exposed, which is small. Other studies have also produced low numbers, such as this. The odds ratios for actual smokers are far higher.

This is about relative risk. It is certainly possible for a particular exposed non-smoker to be more affected than a particular smoker (as someone betting in roulette can win with 0 and somebody else lose on red), but overall smoking directly is a far greater risk than exposure to secondhand smoke.

  • Good link but it only covers lung cancer. Jose’s answer suggests that the overall danger due to passive smoke is much more substantial. – Konrad Rudolph Jul 8 '11 at 11:20
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    @Konrad: No - My second link says "The American Heart Association, the California Environmental Protection Agency, and the US surgeon general have concluded that the increase in coronary heart disease risk due to environmental tobacco smoke is 30% (relative risk 1.30). Meta-analyses of epidemiological studies have reported summary relative risks (95% confidence intervals) of 1.30 (1.22 to 1.38), 1.25 (1.17 to 1.32), and 1.25 (1.17 to 1.33) for coronary heart disease", the same as Jose's. 30% sounds a lot, but is the same as 1.3 relative risk and is small. – Henry Jul 8 '11 at 19:22
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The related question has already established the overall dangers of secondhand smoking. I'll focus on the claim that it's likely or possible that secondhand smoke can cause more damage to the inhaler than the smoker.

The British Lung Foundation claims that it is more dangerous to the inhaler in this manner

Passive smokers inhale smoke breathed in and out by smokers. They also breathe in the smoke from the burning tips of cigarettes. This smoke contains more of the harmful chemicals than the smoke which has passed through the cigarette filter.

To add more from Joe Zasadzinski a UCSB professor of chemical engineering who researched this

Second hand smoke—the fumes and particulate matter, both drifting directly from burning cigarettes, cigars, and pipes (sidestream smoke) and exhaled by smokers (mainstream smoke)—contains more than 5,000 chemical compounds, including the same multitude of carcinogens and toxins inhaled by smokers, including carbon monoxide, cyanide, benzene, formaldehyde, and arsenic. (It’s a Group A carcinogen, along with asbestos, benzene, arsenic, and radon…)

“The chemistries of primary and second-hand smoke are basically the same,” Zasadzinski says, “although “people argue about concentrations a lot—about who gets more.” When they suck on cigarettes, smokers are, of course, intending to inhale a hefty hit of nicotine-laden smoke. However “the smoker has a filter on his or her end of the cigarette,” Zasadzinski points out, “but there’s no filter on the secondhand smoke that comes out the other end. It’s tough to say who gets the worst of it—the active smoker or the passive bystander.”

Regular smokers, however, develop some degree of resilience to the persistent assaults on their lungs, notes Kamlesh Asotra of California’s Tobacco-Related Disease Research Program (TRDRP). Non-smokers don’t, so second hand smoke causes more damage to their lungs than direct smoke does to smokers, Asotra says. (TRDRP disperses funds from state cigarette taxes to researchers—including Zasadzinski.)

To look at the effects of second-hand smoke, Zasadzinski, working with Patrick Stenger and Coralie Alonso, also of UCSB’s Department of Chemical Engineering, and researchers at UCLA and UC Davis, focused on a crucial component of the respiratory system: the thin film of liquid on the inside of the lungs. This epithelial lining fluid helps the lungs function and protects them from damage. “If you smoke or you’re around smoker, this is the first place the smoke will hit…” Zasadzinski says.

To study how second hand smoke affects lung surfactants, Zasadzinski and his colleagues used biologically-based replacement surfactants in a lab setup that replicates how smoke interacts with the fluid lining of the lungs—“a very, very elegant” method of mimicking what happens in a living lung, Asotra says.

The researchers produced second-hand smoke by burning cigarettes in controlled conditions using a “smoking machine” at UC Davis’ Institute of Toxicology and Environmental Health. They exposed purified water to this smoke for six hours, to create a tainted brew that they then used to test the effects of second-hand smoke on replacement lung surfactants. Zasadzinski and his colleagues reported their results recently in the international journal Biochimica et Biophysica Acta.

The extent of the smoke damage to surfactants was “very surprising,” Zasadzinski says. The researchers focused on two proteins that are important in the surfactant function, and found they were both “really badly chewed up” by second-hand smoke. Smoke exposure changed the chemical composition and structure of the surfactants in the study—most likely by damaging crucial proteins

This will highly depend on the level of exposure to the smoke, time spent daily in such exposure, and in the case of "smoke from the burning tips" the proximity to such "burning tips". How much time would a family member be spending next to the smoker's cigarette each day?

I cannot find a more accurate article quoting Kamlesh Asotra and whether any scientific study was carried out to prove this statement, though he has been quoted in this Berkeley study on Third Hand Smoke

Now for some overall stats that I came across, a study on Environmental tobacco smoke and cardiovascular disease. A position paper from the Council on Cardiopulmonary and Critical Care, American Heart Association AE Taylor, DC Johnson and H Kazemi Office of Scientific Affairs, American Heart Association, Dallas, TX 75231-4596. quotes

The risk of death due to heart disease is increased by about 30% among those exposed to environmental tobacco smoke at home and could be much higher in those exposed at the workplace, where higher levels of environmental tobacco smoke may be present. Even though considerable uncertainty is a part of any analysis on the health affects of environmental tobacco smoke because of the difficulty of conducting long-term studies and selecting sample populations, an estimated 35,000-40,000 cardiovascular disease-related deaths and 3,000- 5,000 lung cancer deaths due to environmental tobacco smoke exposure have been predicted to occur each year

Some more recent studies in terms of numbers are available and a report of a scientific refutal on the effects of passive smoking which seems to be biased and incorrect.

This link states about lung cancer alone, but does not cover the gamut of other diseases non-smokers can be affected by

The relative risk of lung cancer among active smokers is about 17, while the relative risk of lung cancer among passive smokers is about 1.3

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    The problem with arguments about non-smokers breathing in various compounds, such as smoke from the end of the cigarette, is that the smoker holding the cigarette is consistently closer to the cigarette so must be getting more of these compounds in addition to their inhaled smoke. – Rory Alsop Jul 8 '11 at 13:27
  • @Rory Not necessarily, since they blow the smoke away from themselves. But of course this is difficult to speculate about. Only measuring can give any certainty. – Konrad Rudolph Jul 8 '11 at 14:19
  • @Konrad - Rory was talking about the smoke from the burning tip of the cigarette, not the exhaled smoke. I tend to agree with him. – JohnFx Jul 10 '11 at 1:43
  • @JohnFx I’m aware of that. I was trying to find rationales for why the original argument might still hold, and the smokers are blowing all the smoke away from themselves, including that from the cigarette’s tip. – Konrad Rudolph Jul 10 '11 at 7:08

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